Late 17th – Mid 18th Century Mineralogy (and a little Cosmology)

Structure of knowledge in the 18th century

• Reflected in Diderot’s classification of knowledge for the Encyclopedie.
  • History: descriptive
  • Philosophy: interpretive, explanations
  • Poetry: creative
• Natural history separated from natural philosophy

The Cosmologists “Theories of the Earth”

• Popular from mid-17th into earliest 19th centuries
• Attempt to explain earth history in an overarching way
  • Insufficient knowledge
  • Changed over time
• Contributions include
  • Strong move away from Scriptural time scale; usually consider natural history as far longer (Buffon being the extreme)
  • Use natural processes and increasing observational information

Minerals and rocks

• Aristotle’s influence still strong in later 17th century
  • Chemists regarded Aristotle’s elements (water, fire) are the main agents for lab investigations
  • Believed that minerals had once been fluid and later rendered solid by removal of heat or water
• Classification became more chemistry based.
  • Four classes
    • Salts and Bitumens: congealed juices
    • Metals
    • Earths and Stones
    • Sulfurs
  • Analysis using Bunsen Burner and reactions with water
• Textural division
  • Mixst: compound of unlike parts that can not be distinguished
  • Aggregate: mixture of unlike parts that can be distiguished
• Consolidation materials
  • Concretion: remove water
  • Congelation: heating or cooling
  • Crystallization: precipitation from water
  • Petrification: replacement of organic matter by stony or metallic matter

Natural Waters

• Contain dissolved material that can make some stones
• Little silica in oceans or springs
• Sea level falling in the Baltic

“Archaic Time Scale”)

• Primary
  • High elevations – mountains
  • Underlie all the other strata
  • Crystalline rocks: granite, schist, phyllite, marble, quartzite
  • No real dip or widely variable, even vertical
  • No fossils
• Secondary
  • Intermediate elevations on flanks of primary
  • Overlie Primary, overlain by Tertiary
  • Steep dip next to Primary, flattens at lower elevations
  • Mixture of rocks
    • Crystalline: gypsum, limestone, basalt
    • Particulate: sandstone, breccia, shale
  • Usually fossiliferous
• Tertiary
  • Low elevations
  • Overlie and onlap base of Secondary
  • Flat-lying
  • Less consolidated, largely particulate rocks
  • Fossiliferous
• Alluvial and Volcanoes
  • Youngest deposits
  • Superficial deposits: alluvium, modern volcanics

Standard knowledge circa 1760

• Study the earth as a natural object
• Figured stone or fossils are organic in origin
• Minerals classification shifted from Aristotle to a chemical basis
  • Use reactions with water and flame to help identify
• Rocks made up of minerals
  • Various consolidation processes rely on water or heat
  • Mixsts and aggregates reflect different sized of constituents
• Rocks have varied origins
  • Crystalline = precipitates
    • Granite, schist, phyllite: from high temperature melts
    • Gypsum, limestone: from dissolved material in water
  • Stony = particulate, clastic
    • Sandstone, breccia, shale
  • Some would be problematic
• Rocks arranged in the “Archaic Time Scale” (see above)
  • Primary
  • Secondary
  • Tertiary
  • Alluvial and Volcanoes: young
• We overlooked two things (think of these a “news flashes“)
  • Sea level falling in Scandinavia
  • Some dissolved silica in trace amounts in some springs